Olefins, also commonly known as alkenes, are important items of commerce. Their many applications include employment as intermediates in the manufacture of detergents, as more environmentally friendly replacements where refined oils might otherwise be used, as monomers, and as intermediates for many other types of products. An important subset of olefins are olefin oligomers, and one method of making olefin oligomers is via oligomerization of ethylene, which is a catalytic reaction involving various types of catalysts.
Examples of catalysts used commercially in polymerization and oligomerization of olefins include alkylaluminum compounds, certain nickel-phosphine complexes, and a titanium halide with a Lewis acid, such as diethylaluminum chloride. Some examples of catalysts, and in particular transition metal catalysts, employed in ethylene polymerization and oligomerization may be found in U.S. Pat. Nos. 5,955,555, 6,103,946, 6,683,187, WO 03/011876, WO 02/28805, and WO 01/58874, which are incorporated herein by reference.
Selective 1-hexene (S1H) catalysts are another example of catalysts employed in the production of olefins. S1H catalysts are designed to be selective for production of 1-hexene. Examples of such S1H catalysts may be found in U.S. Pat. Nos. 6,455,648, 6,380,451, 5,986,153, 5,919,996, 5,859,303, 5,856257, 5,814,575, 5,786,431, 5,763,723, 5,689,028, 5,563,312, 5,543,375, 5,523,507, 5,470,926, 5,451,645, and 5,438,027, which are incorporated herein by reference.
Applications and demand for olefin polymers and oligomers continue to multiply, and competition to supply them correspondingly intensifies. Thus, additional novel and improved catalysts, and methods of olefin polymerization and oligomerization, are desirable.